Among other things, hot-formed cams are already used for assembling composite camshafts. Depending on the joining or assembly principle, according to which the cams are fixed on a shaft or a shaft tube, as well as the component and assembly tolerances to be observed, these hot-formed cams are nowadays subjected to subsequent mechanical processing, i.e., machining, in the cam bore and, in part, on the plane surfaces of the cam. This processing is required in order to limit the position errors between the cam bore and the cam outside contour created during hot-forming because this error manifests itself in the form of an oversize on the contour of the cam after the assembly and needs to be subsequently removed by grinding. The end faces (plane surfaces) are processed in order to reduce axial run-outs, i.e., angle errors of the end faces referred to the bore axis, such that the entire width of the cam is used as a running surface. The end faces (plane surfaces) are also processed in order to prepare flange geometries if the cam is realized in the form of a collared or flanged cam with an adjacent collar or flange.
The end measures of the cam bore required for thermally joining or axially pressing the cam to/on a tube are nowadays achieved by means of precision turning (e.g., hard turning) or internal grinding of the cam bore. In addition, insertion chamfes required for mechanically joining the cams with an axially knurled shaft or for pushing the cams on raised cam seats on a shaft are also turned or ground on the cam bores. Cams that are joined to a shaft tube by means of internal high-pressure forming of the shaft tube were line-bored until now in order to achieve a more precise position of the bore relative to the cam outside contour and to realize the joining gap with close tolerances.
The disadvantages of the preparatory machining of the cams can be seen in the cost-intensive material removal process, in which it is difficult to machine the cam in a defined fashion over its cam outside contour, as well as the expenditures for the technical measurements required for checking the result of the mechanical processing.